The quality of rainwater collected in polyvinyl chloride (PVC) tanks from six trial roofs (glazed tile, pre-painted steel and aluminium-zinc coated steel, each with and without uncoated lead flashing) was monitored for nine months. Samples of water and sediment were collected at three monthly intervals and analysed for concentrations of metals (Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn), in order to determine the influence of roof materials and uncoated lead (Pb) flashing upon metal contamination within the tanks. Lead concentration in tank water exceeded Australian Drinking Water Guidelines for all roof types where there was lead flashing. Lead flashing also contributed to contamination of tank sediments. In all cases, pH was low which contributed to a large proportion of lead being in the dissolved form.

Understanding microorganism levels in urban runoff is essential for appropriate storm-water management, especially when storm-water is utilized by humans. An Escherichia coli monitoring program was conducted at four urban catchments in Melbourne, Australia. Simple and multiple correlation analyses were conducted that related climatic, rainfall, storm-water runoff, and other water-quality characteristics with the event mean concentrations (EMCs) of E. coli. Also, several existing and modified storm-water-quality models were tested against the measured storm-water E. coli levels to determine whether existing storm-water models could be used for prediction. The key findings are that source, growth, and removal of microorganisms are more important than wash-off and transport processes during wet weather since the most influential factors for E. coli EMC levels are (1) antecedent catchment conditions, such as vapor pressure prior to an event; (2) nutrient levels in storm water, such as ammonium, total phosphorus, and total nitrogen levels. However, rainfall intensity, which was found to be the most important transport-related variable (although less significant than the aforementioned build-up parameters), may also be considered in EMC prediction. DOI: 10.1061/(ASCE)EE.1943-7870.0000674. (C) 2013 American Society of Civil Engineers.

Accurate estimation of the levels of microorganisms in urban stormwater is needed for stormwater harvesting and to ensure that our streams and bays are safe for recreational uses. The aim of this research was to develop and test a simple urban stormwater microorganism model (Micro-Organism Prediction in Urban Stormwater - MOPUS) which is spatially lumped and coupled to a rainfall runoff model. The microorganism model has surface and subsurface components to simulate build-up and wash-off of microorganisms from the impervious surfaces of the catchment and the stormwater pipes, respectively. The rainfall-runoff model simulates processes from both pervious and impervious surfaces. Both models are conceptual and represent important processes in a simplified manner, thereby limiting the number of calibration coefficients (five for each model) while maintaining accuracy. The coupled model has been tested using a large Escherichia coli (E. coli) dataset collected from four urban catchments in Melbourne, Australia. For each catchment, around 20 well sampled pollutographs were available. Reasonably good predictions were obtained at each site for both instantaneous flow rates (Nash Sutcliffe E between 0.62 and 0.89) and E. coli concentrations (E = 0.25-0.45). Event E. coli peaks (E = 0.42-0.75), E. coli loads (E = 0.48-0.86) and event mean E. coli concentrations (E = 0.56-0.76) were also well estimated. In general, it has been demonstrated that, with further development and testing, MOPUS appears capable of reliable predictions of E. coli discharges from urban stormwater systems, allowing its use as a planning tool for urban catchments. (C) 2011 Elsevier B.V. All rights reserved.

This paper reports the results of laboratory experiments investigating the effect of rainwater tank design on re-suspension of accumulated sediment and the resultant water quality. Twenty-eight different configurations that represented different tank designs in combination with various water levels and quantities of stored sediment were investigated. Re-suspension of sediment was observed during all experiments regardless of the position of the top inlet (whether side or centrally positioned), position of the bottom outlet (50, 100, 200, 400 and 600 mm above the base of the tank), the shape of the tank base (flat or conical), the initial water level in the tank (empty, quarter full or half full), the sediment thickness (10 or 20 mm), the particle size (two particle size ranges) or inflow rate (0.5 or 1.0 L/s). The re-suspended sediment contaminated the out-flowing water, and the greatest impact (worst outcome for water quality) was observed for a centrally located top inlet and an outlet located 50 mm above the tank base. The least contamination of the out-flowing water was observed when the inlet was positioned on the side of the tank. To reduce the potential for contamination of the out-flowing water, it is recommended that rainwater tanks preferably have a side inlet and a conical base, that the sediment thickness in the tank be maintained at low levels by regularly cleaning the tank, and that the tank water be not used during or immediately following rainfall events.

This paper presents the sensitivity analysis of a newly developed model which predicts microorganism concentrations in urban stormwater (MOPUS—MicroOrganism Prediction in Urban Stormwater). The analysis used Escherichia coli data collected from four urban catchments in Melbourne, Australia. The MICA program (Model Independent Markov Chain Monte Carlo Analysis), used to conduct this analysis, applies a carefully constructed Markov Chain Monte Carlo procedure, based on the Metropolis-Hastings algorithm, to explore the model's posterior parameter distribution. It was determined that the majority of parameters in the MOPUS model were well defined, with the data from the MCMC procedure indicating that the parameters were largely independent. However, a sporadic correlation found between two parameters indicates that some improvements may be possible in the MOPUS model. This paper identifies the parameters which are the most important during model calibration; it was shown, for example, that parameters associated with the deposition of microorganisms in the catchment were more influential than those related to microorganism survival processes. These findings will help users calibrate the MOPUS model, and will help the model developer to improve the model, with efforts currently being made to reduce the number of model parameters, whilst also reducing the slight interaction identified.

Stormwater harvesting is a relatively new concept which has developed using traditional stormwater management practices as well as water resourcing and holistic water management concepts. While stormwater harvesting systems have been designed and constructed in the past, the planning and design processes have not followed an integrated approach. This paper addresses this issue and describes a decision-making framework (DMF) that determines the most appropriate stormwater harvesting scheme option based primarily on technical feasibility and financial costs with a focus on neighbourhood-scale development. A case study of an existing urban area in the suburb of Sunshine in Melbourne, Australia, was conducted to demonstrate the DMF. Comparison of all stormwater harvesting scheme options determined that while one scheme option was the most effective option in terms of cost, reliability, quantity of stormwater used and end uses met, several other options could also be examined further for detailed analysis.

The water from rainwater tanks has often been found to have high lead concentrations, in some cases exceeding potable water guidelines. These high lead concentrations were previously linked to the presence of lead flashing on roofs and proximity of roofs to roads and industry. In this study, water and sediment samples were collected from 52 tanks across the Melbourne metropolitan area along with information about the tanks, roofs and the surrounding environment. The results were analysed to identify significant relationships between lead concentrations in tank water, tank sediments and a range of variables collected. Water quality in 14 of the 52 tanks sampled exceeded Australian Drinking Water Guidelines (ADWG) for lead concentrations. It was found that lead flashing, prevailing winds, proximity to roads and commercial zones had statistically significant relationships with lead concentrations in rainwater tanks, thus implying that no single source is the sole cause of high lead concentrations.

Although water-quality monitoring programs have been widely used to identify and understand the level of pollution in urban stormwater systems, these data are often used without due consideration of the inherent uncertainties contained within these measurements. This study focuses on the uncertainties associated with the monitored levels of Escherichia coli, a common microbial indicator, in urban stormwater. Four sites located in Melbourne, Australia, were used to assess the uncertainty of six stormwater flow and E. coli variables: (1) discrete E. coli concentration, (2) stormwater flow rate, (3) stormwater event volume, (4) event mean concentration (EMC) of E. coli (i.e. a flow-weighted average of an event's E. coli concentrations), (5) E. coli load for each measured event, and (6) site mean E. coli concentration (SMC) (i.e. a volume-weighted average of the E. coli EMCs). Uncertainties of discrete E. coli samples were greater than 30%, while the uncertainty in stormwater flow measurements averaged greater than 97%, mainly due to the high uncertainties in measurements of very low flows. Propagation of these uncertainties, through their respective formulas, found that E. coli EMC uncertainties varied between 10% and 52% and that uncertainties relating to SMC estimates ranged from 35% to 55%. These results show the importance of considering uncertainty when using monitored data sets for any application, including those relating to stormwater management decisions. Suggestions are made about how to increase the accuracies of E. coli monitoring in urban stormwater and how to balance the different sources of uncertainties so that the overall combined uncertainties are minimised while keeping costs at a minimum.

Due to the need to consider rainwater tanks as an option within urban water resources policy development and strategic planning within Australia, modelling tools are used to predict their yield and volumetric reliability. The accuracy of the estimate of these performance measures is important as they form the basis of the predicted potable supply reduction level. This paper investigates how temporal and spatial lumping impacts on the estimated yield and volumetric reliability of suburban rainwater tank systems. This question is of interest because the overall behaviour of a group of household rainwater tank systems, comprising a diverse mix of roof catchment areas, tanks storage capacities, and end use demand characteristics, is not identical to the behaviour of a single household rainwater tank system which has the mean characteristics of the group of rainwater tank systems. The analysis presented in this paper suggests that the spatial averaging of multiple rainwater tank characteristics systematically predicts greater yield and volumetric reliability. The magnitude of this variation is significant enough to warrant further attention. Using a daily time step (temporal lumping) and spill before yield, in combination with a depression storage depth of >0, produced larger estimates of yield and volumetric reliability relative to using a 6 minute time step. In comparison, using a daily time step, in combination with a depression storage depth of 0, produced insignificant differences in yield and volumetric reliability relative to using a 6 minute time step, except in the case of the very small tank system tested.

Pathogenic microorganisms have been identified as the main human health risks associated with the reuse of treated urban stormwater (runoff from paved and unpaved urban areas). As part of the Smart Water initiative (Victorian Government, Australia), a collaborative evaluation of three existing integrated stormwater recycling systems, and the risks involved in non-potable reuse of treated urban stormwater is being undertaken. Three stormwater recycling systems were selected at urban locations to provide a range of barriers including biofiltration, storage tanks, UV disinfection, a constructed wetland, and retention ponds. Recycled water from each of the systems is used for open space irrigation. In order to adequately undertake exposure assessments, it was necessary to quantify the efficacy of key barriers in each exposure pathway. Given that none of the selected treatment systems had previously been evaluated for their treatment efficiency, experimental work was carried out comprising dry and wet weather monitoring of each system (for a period of 12 months), as well as challenging the barriers with model microbes (for viruses, bacteria and parasitic protozoa) to provide input data for use in Quantitative Microbial Risk Assessment.

The degradation of aquatic ecosystems due to hydrologic and water quality impacts of urbanization, combined with increasing water scarcity, has generated increasing interest in the harvesting of urban storm water. This paper reviews the rationale for integrated storm water treatment and harvesting and synthesizes recent advances and trends and knowledge gaps that limit its application. Storm water harvesting is shown to be a viable alternative water supply and to provide a potential solution to the increases in runoff frequency and peak flows that occur as a result of catchment urbanization. In general, treatment technologies for storm water harvesting have been adapted from existing "water-sensitive urban design" approaches, with limited use of traditional water supply and wastewater technologies. Risk management is often lacking, in part due to a lack of relevant guidance. Reported performance shows variable levels of potable water savings, with cases of up to 100% substitution recorded. Costs of storm water harvesting systems are shown to be inversely related to their scale. The limited cost data show the importance of context, with the harvested water costing more or less than alternative supplies, depending on the cost of the alternative. Limited data exist on environmental benefits, such as reductions in pollutant loads and flow peaks. Implementation of storm water harvesting systems is impeded by inadequate data on risk, lifecycle costs, externalities, and water-energy tradeoffs. Furthermore, retrofit of storm water harvesting into existing urban areas is proving to be a challenge, creating an urgent need for specific technologies for use in retrofit situations.

Using a water balance modelling framework, this paper analyses the effects of urban design on the water balance, with a focus on evapotranspiration and storm water. First, two quite different urban water balance models are compared: Aquacycle which has been calibrated for a suburban catchment in Canberra, Australia, and the single-source urban evapotranspiration-interception scheme (SUES), an energy-based approach with a biophysically advanced representation of interception and evapotranspiration. A fair agreement between the two modelled estimates of evapotranspiration was significantly improved by allowing the vegetation cover (leaf area index, LAI) to vary seasonally, demonstrating the potential of SUES to quantify the links between water sensitive urban design and microclimates and the advantage of comparing the two modelling approaches. The comparison also revealed where improvements to SUES are needed, chiefly through improved estimates of vegetation cover dynamics as input to SUES, and more rigorous parameterization of the surface resistance equations using local-scale suburban flux measurements. Second, Aquacycle is used to identify the impact of an array of water sensitive urban design features on the water balance terms. This analysis confirms the potential to passively control urban microclimate by suburban design features that maximize evapotranspiration, such as vegetated roofs. The subsequent effects on daily maximum air temperatures are estimated using an atmospheric boundary layer budget. Potential energy savings of about 2% in summer cooling are estimated from this analysis. This is a clear return on investment of using water to maintain urban greenspace, whether as parks distributed throughout an urban area or individual gardens or vegetated roofs. Copyright (C) 2007 John Wiley & Sons, Ltd.

Accurate estimation of the levels of microorganisms in urban stormwater is needed for stormwater harvesting and, possibly more importantly, to ensure that our streams and bays are safe for recreational uses. The aim of this research was to develop and test a simple, yet accurate, urban stormwater microorganism model. The microorganism model is spatially lumped and coupled to a simple rainfall runoff model. The surface and subsurface components of the new microorganism model simulate build-up and wash-off of microorganisms from (a) the impervious surfaces of the catchment and (b) the stormwater pipes, respectively. The model has been tested using a large Escherichia coli dataset collected from four urban catchments in Melbourne, Australia. For each catchment, around 20 well sampled pollutographs were available. The results of the model are promising, with good predictions in both instantaneous flow rates and E. coli concentrations. Furthermore, event E. coli peaks and loads were also estimated with high accuracy together with event mean E. coli concentrations. The model is undergoing further testing and development, including sensitivity, validation and uncertainty analyses.

Recently, it has become apparent that stormwater harvesting has the potential to play a significant role in the sustainable management of water resources. However, it has been recognised that uncertainties concerning the operational performance of existing stormwater harvesting systems and also the lack of appropriate design standards are barriers to the widespread adoption and utilisation of stormwater harvesting. In this study, we gathered design and operational information regarding three stormwater harvesting systems located in Melbourne, as well as undertaking water quality and quantity monitoring. It was found that the design objectives of each system were developed in order to meet a range of environmental, social and economic outcomes, and while most of these objectives were met, some were rather qualitative and so were difficult to assess. The design of each harvesting system did not represent what was built and this is likely to be limiting operational performance. The ongoing drought has severely impacted on the volume of stormwater harvested from the two smaller systems, however, recent winter/spring rainfall has increased the volume of stormwater in storage. In comparison, the larger system has been able to provide significant amounts of stormwater during the very dry summer of 2007 and throughout the year. Preliminary water quality monitoring indicated that systems featuring WSUD devices are able to improve the water quality (in terms of TSS, TN and TP) of stormwater. Importantly, it appears that systems that do not have disinfection will more frequently have E. coli levels that exceed 10 orgs/100 mL.

Urban water systems contribute to climate change both directly through the fugitive greenhouse gas (GHG) emissions associated with water storage reservoirs and wastewater treatment processes, and indirectly through significant energy and materials consumption. This paper presents the findings of an investigation of the GHG emissions associated with operating a case study urban water system in Melbourne, Australia. It was revealed that the appliances associated with the residential end uses of water were responsible for significantly more GHG emissions than all upstream and downstream operations. These findings led to the conclusions that any project seeking to minimise the energy consumption and GHG emissions associated with urban water systems should: (a) consider the whole system, including the end uses of water, in a holistic application of life cycle thinking, and (b) focus on reducing the energy and water consumption associated with the end uses of water, since this will yield multiple benefits upstream, downstream and at the point of use.